US 7848434 B2 Abstract A channel estimator and a related method for smoothing channel responses of a multi-carrier system. The channel estimator includes a channel response computing circuit for computing at least one of a target channel estimation and a reference channel estimation by utilizing a computing algorithm, wherein the target channel estimation and the reference channel estimation corresponds to a sub-carrier channel respectively.
Claims(16) 1. A channel estimator for evaluating a channel response of a sub-carrier in a multi-carrier communication system, the channel estimator comprising:
a channel response computing circuit for processing both a target channel estimating value and a reference channel estimating value according to a computing algorithm to generate a smoothed target channel response by generating a channel condition indicator, wherein the target channel estimating value and the reference channel estimating value respectively correspond to sub-carrier channels in the multi-carrier communication system; and
the channel condition indicator being generated based on multiplying a channel strength indicator corresponding to the magnitude of the target channel estimating value and a channel varying indicator utilizing the target channel estimating value and the reference channel estimating value.
2. The channel estimator of
a one-shot channel estimating circuit, electrically connected to the channel response computing circuit, for generating a plurality of one-shot target channel estimating values according to different time intervals and a plurality of one-shot reference channel estimating values according to different time intervals, the one-shot channel estimating circuit or the channel response computing circuit generating the target channel estimating value and the reference channel estimating value according to the one-shot target channel estimating values and the one-shot reference channel estimating values, respectively.
3. The channel estimator of
a one-shot channel estimating circuit, electrically connected to the channel response computing circuit, for generating at least two one-shot target channel estimating values according to different time intervals, and the channel response computing circuit generating a channel noise indicator by processing the one-shot target channel estimating values according to the computing algorithm, then the channel response computing circuit generating the smoothed target channel response by processing the target channel estimating value according to the channel noise indicator.
4. The channel estimator of
5. The channel estimator of
6. The channel estimator of
7. The channel estimator of
8. The channel estimator of
9. The channel estimator of
10. A channel response smoothing method for smoothing a channel response of a sub-carrier in a multi-carrier communication system, the channel estimating method comprising:
utilizing a computing algorithm to process both a target channel estimating value and a reference channel estimating value in order to generate a computing result, wherein the target channel estimating value and the reference channel estimating value correspond to a first sub-carrier channel and a second sub-carrier channel of the multi-carrier communication system, respectively, wherein utilizing comprises multiplying a channel strength indicator and a channel varying indicator according to the computing algorithm to generate the computing result, the computing result corresponding to a channel condition indicator; wherein the channel strength indicator corresponds to the magnitude of the target channel estimating value and the channel varying indicator utilizes the target channel estimating value and the reference channel estimating value; and
processing the target channel estimating value according to the computing result to generate a smoothed target channel response.
11. The channel response smoothing method of
receiving a plurality of one-shot target channel estimating values and a plurality of one-shot reference channel estimating values, the one-shot target and reference channel estimating values being generated according to different time intervals; and
generating the target channel estimating value and the reference channel estimating value by respectively processing the one-shot target channel estimating values and the one-shot reference channel estimating values according to the computing algorithm.
12. The channel response smoothing method of
receiving at least two one-shot target channel estimating values being generated according to different time intervals, each one-shot target channel estimating value and the target channel estimating value corresponding to the first sub-carrier channel, each one-shot reference channel estimating value and the reference channel estimating value corresponding to the second sub-carrier channel; and
comparing a difference between the one-shot target channel estimating values with a threshold value according to the computing algorithm to generate the computing result, the computing result corresponding to a channel noise indicator.
13. The channel response smoothing method of
14. The channel response smoothing method of
comparing a difference between the target channel estimating value and the reference channel estimating value with at least one threshold value according to the computing algorithm to generate the computing result, the computing result corresponding to a channel varying indicator.
15. The channel response smoothing method of
processing the channel strength indicator and the channel varying indicator according to the computing algorithm to generate a channel condition indicator; and
comparing the channel condition indicator with at least one threshold value according to the computing algorithm to generate the computing result, the computing result corresponding to a set of smoothing filtering coefficients.
16. A channel estimator comprising:
a channel response computing circuit for smoothing a channel response of a sub-carrier in a multi-carrier communication system, the channel response computing circuit processing both a target channel estimating value and a reference channel estimating value according to a computing algorithm,
wherein the target channel estimating value and the reference channel estimating value correspond to two different sub-carrier channels respectively of the multi-carrier communication system,
the channel response computing circuit further comprising a channel response calibrating unit for calibrating the target channel estimating value to generate a smoothed target channel response according to smoothing filter coefficients selected based on a channel condition indicator,
wherein the channel condition indicator is based on multiplication of a channel strength indicator that corresponds to the magnitude of the target channel estimating value and a channel varying indicator that utilizes the target channel estimating value and the reference channel estimating value.
Description 1. Field of the Invention The present invention relates to a channel estimator and related method, and more particularly, to a channel estimator and related method for smoothing a channel response of a multi-carrier communication system. 2. Description of the Prior Art The communication channel between a receiver and a transmitter delays and attenuates the transmitted signal. As a result, the amplitude of a received signal is smaller than the amplitude of the corresponding transmitted signal, and the phase of the transmitted signal is different from the phase of the received signal. To alleviate the phenomenon mentioned above, an equalizer and a channel estimator are implemented in the receiver to restore the attenuated and delayed signal received from the communication channel. Firstly, the channel estimator evaluates the attenuation and the delay of the received signal according to a preamble of the received packet, where the preamble is a series of known symbols. That is, the channel estimator generates a channel estimating value by comparing the received signal with the known symbols. The operation of the channel estimator is shown in the following equation:
In the equation (1), R denotes the received signal, X denotes the known preamble, and H′ denotes the channel estimating value. After a plurality of channel estimating values H′, H″, . . . ,H′ In the multi-carrier communication system, such as an ultra-wideband (UWB) communication system, the channel responses of two adjacent sub-carriers are correlated such that the channel responses of different sub-carriers will form a smoothed curve in a spectrum. Unfortunately, the wireless communication system suffers from noise. The noise reduces the signal to noise ratio (SNR) of the wireless communication system. Owing to the noise of the communication channel, the estimated channel responses are incorrect. The resulting curve containing the incorrect channel responses displays jitters. Furthermore, it is not possible to utilize these incorrect channel responses in an effort to restore the received signal in hopes of generating the equalized signal. It is therefore an objective of the claimed invention to provide a channel estimator and related method capable of smoothing a channel response of a multi-carrier communication system in order to solve the above-mentioned problem. According to an embodiment of the claimed invention, a channel estimator for evaluating a channel response of a sub-carrier in a multi-carrier communication system is disclosed. The channel estimator comprises: a channel response computing circuit for processing one of a target channel estimating value and a reference channel estimating value according to an computing algorithm to generate a smoothed target channel response, wherein the target channel estimating value and the reference channel estimating value correspond to a sub-carrier channels in the multi-carrier communication system, respectively. According to an embodiment of the claimed invention, a channel response smoothing method for smoothing a channel response of a sub-carrier in a multi-carrier communication system is disclosed. The channel estimating method comprises: utilizing a computing algorithm to process one of a target channel estimating value and a reference channel estimating value to generate a computing result, wherein the target channel estimating value and the reference channel estimating value corresponding to a first sub-carrier channel and a second sub-carrier channel of the multi-carrier communication system, respectively; and processing the target channel estimating value according to the computing result to generate a smoothed target channel response. These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. Please refer to In the preferred embodiment, the channel response computing circuit Please keep referring to In the preferred embodiment, the channel environment estimating unit
In addition to generating the channel noise indicator CNI
In the equation (3) and equation (4), γ In the preferred embodiment, the channel environment estimating unit Please note that the method for generating the channel condition indicator CCI
In addition to generating the channel noise indicator CNI Please note that the functional diagram shown in Please refer to Step Step Step Step Step Step Step Please note the following two items regarding the computing algorithm mentioned above. First, the computing algorithm may comprise a plurality of equations. Second, the forms of the equations are not limited. As shown in In summary, the channel estimator compares more than one one-shot channel estimating values to evaluate the channel noise. Besides, the channel estimator processes the channel estimating values corresponding to different sub-channels, respectively, to generate a more precise smoothed channel response. As a result, the ability to alleviate the noise of the communication system rises at the same time. Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims. Patent Citations
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